Forming protective packaging for various articles of different sizes and shapes is a common problem in the packaging industry. In many circumstances, various articles of different sizes and shapes have to be packaged within generally square or rectangular packing cartons for handling and shipment. When the size and shape of the article to be packaged varies from such rectangular or square shapes, a typical solution is to include some sort of cushioning material to fill up the otherwise empty space represented by the difference in shape of the article and that of the container.
In one such prior packaging method, the cushioning material comprises a loose, friable material which is poured into the package to completely surround the articles. In another method, the articles are wrapped in sheets of cushioning material. Still another method currently in use involves foam-in-place packings, wherein a package which comprises a plastic bag containing a foamable composition, is placed in the carton so as to surround the product. The foam thereafter expands in the bag and hardens. Foamable compositions of this type are well known in the art, and they are also referred to as foaming agents or foam precursors. Generally these materials are a combination of polymeric materials and either gases or gas-generating compounds. When properly mixed and distributed, gases permeate the polymeric materials, forming the resulting foam.
U.S. Pat. No. 4,674,268 to Gavronsky et al, and which is commonly owned with the present invention, discloses an apparatus for automating the fabrication of foam filled bags of the above described type. In particular, the apparatus disclosed in this prior patent advances a supply of plastic tubing, transversely heat seals the tubing to form individual bags, forms slits across each bag, opens the bags at the slits, and then inserts an injection cartridge laterally into the slits for filling each bag with the desired foamable composition. Also, the seal across the top of each bag may have interruptions, to permit the gas generated during foam formation to escape without disturbing the integrity of the bag.
While the Gavronsky et al apparatus represents a significant improvement over the prior essentially manual bag forming procedures, certain disadvantages remain. In particular, the requirement that the apparatus slit the plastic tubing, then open the bag, and then laterally insert a nozzle and inject the foamable composition into the bag necessitates a rather complicated mechanical system. Also, it is difficult to insure that all of the foamable composition enters the bag, and spillage is a common problem.
It is accordingly an object of the present invention to provide a method and apparatus for forming foam cushions of the described type, and which avoids the above noted disadvantages of the prior art systems.
It is a more specific object of the present invention to provide a method and apparatus for successively forming foam cushions, and which simultaneously fills and fabricates the bags from a pair of webs of plastic film, and which substantially eliminates spillage of the foamable composition.
It is also an object of the present invention to provide an apparatus for forming foam cushions and which is of relatively simple structural design, and which is able to provide gas ventilation openings in each bag by a simple procedure.
It is a further object of the present invention to provide a method and apparatus for forming foam cushions which is easily adapted for use in a totally mechanized operation for packaging one or more articles in a container.
These and other objects and advantages of the present invention are achieved in the embodiments illustrated herein, by the provision of a method and apparatus which includes advancing a pair of webs of plastic film along predetermined paths of travel from respective supply sources, and including guiding the advancing webs into opposing face-to-face contact at a first heat sealing station. At the heat sealing station, the opposing longitudinal side edges of the advancing webs are heat sealed to each other. Periodically, a predetermined amount of a foamable composition is introduced between the pair of webs of plastic film, and so as to be deposited in each bag being formed. Also, the heat sealing of the pair of webs is periodically and momentarily interrupted along at least one of the side edges during the advance of the webs through the first heat sealing station, so as to form at least one unsealed side edge opening for each bag. Finally, the advancing webs are advanced to a second heat sealing station and transversely heat sealed upstream of the unsealed side edge portions, to form a sealed top edge for each successive bag of foamable composition and including severing each bag from the next succeeding bag while forming a sealed bottom edge for the next succeeding bag.
The advance of the pair of webs from the respective supply sources includes advancing the webs in a generally downward direction and in an opposing and converging relationship, and the predetermined amount of foamable composition is introduced from a discharge location which is between the converging webs and in close proximity to the point at which the webs initially contact each other. By this arrangement, the converging webs serve to funnel the foamable composition into the resulting bag to thereby minimize splashing and spillage.